Anaesthesia and Non-Obstetric Surgery in Pregnancy
Highlights
- postponing elective cases until 6 weeks postpartum is recommended (View Highlight)
New highlights added August 13, 2023 at 5:15 PM
- Commonly used preoperative medications, including benzodiazepines or opioids, may be safely offered without concern for fetal cleft palate (View Highlight)
- The second trimester is preferred for non-elective surgery. Patients are considered to be at the lowest risk for preterm delivery, surgical exposure is enhanced as the uterus is lower in the abdomen, and major embryonic development is complete by the eighth week (View Highlight)
- NSAIDs should be avoided after 32 weeks of gestation because of concerns for premature patent ductus arteriosus closure (View Highlight)
- Mucosal friability and oedema occur early in the first trimester and are most prominent in the third trimester.5 Nasal intubation, regardless of trimester, is not recommended, as increased vascularity can cause epistaxis. (View Highlight)
- Respiratory changes begin in the first trimester and continue to have an effect throughout pregnancy. Maternal oxygen consumption increases steadily to meet the demands of the growing fetus. Increased minute ventilation, driven mostly by increased tidal volumes, leads to compensated respiratory alkalosis with a pH nearing 7.44.5 This should guide ventilatory settings to a target Pe′co2 of 3.7–4.3 kPa during general anaesthesia or blood gas analysis. (View Highlight)
- Cardiac output increases by 50% above baseline by the end of the second trimester, which may predispose patients with congenital heart anomalies, heart failure or valve disease to dysrhythmia or worsening heart failure (View Highlight)
- Gastric emptying and acid secretion do not change before labour regardless of the patient’s BMI. (View Highlight)
- Lower oesophageal sphincter tone decreases with progesterone concentrations and reaches a nadir at 36 weeks.5 Combined with the accompanying mechanical displacement of the stomach by the gravid uterus, the patient is at increased risk for regurgitation and aspiration. In addition, 80% of patients can experience nausea and vomiting as early as 4 weeks (View Highlight)
- rapid sequence induction with aspiration prophylaxis should be considered in any trimester if the patient is experiencing nausea, vomiting, pain, infection, and gastro-oesophageal reflux; has a history of hiatus hernia; or has a full stomach (View Highlight)
- Inferior vena cava compression as early as 13–16 weeks has been reported (View Highlight)
- CO2 insufflation confers a higher risk of hypercarbia.7 Hypercarbia, hypotension and hypoxaemia may lead to vasoconstriction and subsequent reduction in uteroplacental perfusion, which may lead to fetal distress.2 Consequences of CO2 pneumoperitoneum can be reduced by keeping insufflation pressures between 12 and 15 mmHg, and maintaining baseline maternal Paco2 and arterial blood pressure (View Highlight)
- Hypotension may be treated with either phenylephrine or ephedrine, as both are safe for use in pregnancy. (View Highlight)
- Cardiac output may reach values 150% above pregnancy baseline immediately postpartum and may take up to 24 weeks to return to normal (View Highlight)
- Maternal heart rate stabilises within 2 weeks (View Highlight)
- The dilutional anaemia seen throughout the pregnancy resolves by 3 weeks postpartum (View Highlight)
- Gastric emptying, volume and pH return to pre-pregnancy levels at 18 h postpartum (View Highlight)